OpenSearch::Transport

The client supports many configurations options for setting up and managing connections, configuring logging, customizing the transport library, etc.

Setting Hosts and Ports

To connect to a specific OpenSearch host and port:

OpenSearch::Client.new host: 'search.myserver.com:8080'

Note: The default port is 9200.

To connect to multiple hosts:

OpenSearch::Client.new hosts: [ { host: 'myhost1', port: 8080 }, { host: 'myhost2', port: 8080 } ]

NOTE: When specifying multiple hosts, you probably want to enable the retry_on_failure option to perform a failed request on another node (see retry_on_failure).

Common URL parts -- scheme, HTTP authentication credentials, URL prefixes, etc -- are handled automatically:

OpenSearch::Client.new url: 'https://username:password@api.server.org:4430/search'

Another way to configure the URL(s) is to export the OPENSEARCH_URL variable.

The client will automatically round-robin across the hosts (unless you select or implement a different connection selector).

Authentication

You can pass the authentication credentials, scheme and port in the host configuration hash:

OpenSearch::Client.new hosts: [
    { host: 'my-protected-host',
    port: '443',
    user: 'USERNAME',
    password: 'PASSWORD',
    scheme: 'https'
    } ]

To pass a custom certificate for SSL peer verification to Faraday-based clients, use the transport_options option:

OpenSearch::Client.new url: 'https://username:password@example.com:9200',
                    transport_options: { ssl: { ca_file: '/path/to/cacert.pem' } }

You can also use API Key authentication

OpenSearch::Client.new(
  host: host,
  transport_options: transport_options,
  api_key: credentials
)

Where credentials is either the base64 encoding of id and api_key joined by a colon or a hash with the id and api_key:

OpenSearch::Client.new(
  host: host,
  transport_options: transport_options,
  api_key: {id: 'my_id', api_key: 'my_api_key'}
)

Logging

To log requests and responses to standard output with the default logger (an instance of Ruby's {::Logger} class), set the log argument to true:

OpenSearch::Client.new(log: true)

To trace requests and responses in the Curl format, set the trace argument:

OpenSearch::Client.new(trace: true)

You can customize the default logger or tracer:

client.transport.logger.formatter = proc { |s, d, p, m| "#{s}: #{m}\n" }
client.transport.logger.level = Logger::INFO

Or, you can use a custom ::Logger instance:

OpenSearch::Client.new(logger: Logger.new(STDERR))

You can pass the client any conforming logger implementation:

require 'logging' # https://github.com/TwP/logging/

log = Logging.logger['opensearch']
log.add_appenders Logging.appenders.stdout
log.level = :info

client = OpenSearch::Client.new(logger: log)

Custom HTTP Headers

You can set a custom HTTP header on the client's initializer:

client = OpenSearch::Client.new(
  transport_options: {
    headers:
      {user_agent: "My App"}
  }
)

You can also pass in headers as a parameter to any of the API Endpoints to set custom headers for the request:

client.search(index: 'myindex', q: 'title:test', headers: {user_agent: "My App"})

client = OpenSearch::Client.new
client.search(index: 'myindex', q: 'title:test', opaque_id: '123456')

The search request will include the following HTTP Header:

X-Opaque-Id: 123456

You can also set a prefix for X-Opaque-Id when initializing the client. This will be prepended to the id you set before each request if you're using X-Opaque-Id. Example:

client = OpenSearch::Client.new(opaque_id_prefix: 'eu-west1')
client.search(index: 'myindex', q: 'title:test', opaque_id: '123456')

The request will include the following HTTP Header:

X-Opaque-Id: eu-west1_123456

Setting Timeouts

To increase the timeout, you can use the request_timeout parameter:

OpenSearch::Client.new request_timeout: 5*60

Connection Selector

By default, the client will rotate the connections in a round-robin fashion, using the {OpenSearch::Transport::Transport::Connections::Selector::RoundRobin} strategy. When the same client would be running in multiple processes (eg. in a Ruby web server such as Thin), it might keep connecting to the same nodes "at once". To prevent this, you can randomize the hosts collection on initialization and reloading:

OpenSearch::Client.new hosts: ['localhost:9200', 'localhost:9201'], randomize_hosts: true

You can implement your own strategy to customize the behaviour. For example, let's have a "rack aware" strategy, which will prefer the nodes with a specific attribute. Only when these would be unavailable, the strategy will use the other nodes:

class RackIdSelector
    include OpenSearch::Transport::Transport::Connections::Selector::Base

    def select(options={})
    connections.select do |c|
        # Try selecting the nodes with a `rack_id:x1` attribute first
        c.host[:attributes] && c.host[:attributes][:rack_id] == 'x1'
    end.sample || connections.to_a.sample
    end
end

OpenSearch::Client.new hosts: ['x1.search.org', 'x2.search.org'], selector_class: RackIdSelector

Retrying on Failures

To retry a failed request on a different host in case of multiple hosts:

OpenSearch::Client.new hosts: ['localhost:9200', 'localhost:9201'], retry_on_failure: true

By default, the client will retry the request 3 times. You can specify how many times to retry before it raises an exception by passing a number to retry_on_failure:

OpenSearch::Client.new hosts: ['localhost:9200', 'localhost:9201'], retry_on_failure: 5

These two parameters can also be used together:

OpenSearch::Client.new hosts: ['localhost:9200', 'localhost:9201'], retry_on_status: [502, 503], retry_on_failure: 10

Reloading Hosts

OpenSearch by default dynamically discovers new nodes in the cluster. You can leverage this in the client, and periodically check for new nodes to spread the load.

To retrieve and use the information from the Nodes Info API on every 10,000th request:

OpenSearch::Client.new hosts: ['localhost:9200', 'localhost:9201'], reload_connections: true

You can pass a specific number of requests after which the reloading should be performed:

OpenSearch::Client.new hosts: ['localhost:9200', 'localhost:9201'], reload_connections: 1_000

To reload connections on failures, use:

OpenSearch::Client.new hosts: ['localhost:9200', 'localhost:9201'], reload_on_failure: true

The reloading will timeout if not finished under 1 second by default. To change the setting:

OpenSearch::Client.new hosts: ['localhost:9200', 'localhost:9201'], sniffer_timeout: 3

NOTE: When using reloading hosts ("sniffing") together with authentication, just pass the scheme, user and password with the host info -- or, for more clarity, in the http options

OpenSearch::Client.new host: 'localhost:9200',
                            http: { scheme: 'https', user: 'U', password: 'P' },
                            reload_connections: true,
                            reload_on_failure: true

Transport Implementations

By default, the client will use the Faraday HTTP library as a transport implementation.

It will auto-detect and use an adapter for Faraday based on gems loaded in your code, preferring HTTP clients with support for persistent connections.

Faraday uses adapters, usually in separate gems, to connect to the HTTP library. You need to make sure that your code refers to both the HTTP library gem and the adapter gem. See this list of Faraday adapters for details.

To use the Patron HTTP, for example, you need to refer to these gems:

gem 'patron'
gem 'faraday-patron'

If you don't use Bundler, you may need to require the libraries explicitly in your code:

require 'patron'
require 'faraday/patron'

Then, create a new client, and the Patron gem will be used as the "driver":

client = OpenSearch::Client.new

client.transport.connections.first.connection.builder.adapter
# => Faraday::Adapter::Patron

10.times do
  client.nodes.stats(metric: 'http')['nodes'].values.each do |n|
    puts "#{n['name']} : #{n['http']['total_opened']}"
  end
end

# => Stiletoo : 24
# => Stiletoo : 24
# => Stiletoo : 24
# => ...

To use a specific adapter for Faraday, pass it as the adapter argument:

client = OpenSearch::Client.new adapter: :net_http_persistent

client.transport.connections.first.connection.builder.handlers
# => [Faraday::Adapter::NetHttpPersistent]

To pass options to the Faraday::Connection constructor, use the transport_options key:

client = OpenSearch::Client.new transport_options: {
    request: { open_timeout: 1 },
    headers: { user_agent:   'MyApp' },
    params:  { :format => 'yaml' },
    ssl:     { verify: false }
}

To configure the Faraday instance directly, use a block:

client = OpenSearch::Client.new(host: 'localhost', port: '9200') do |f|
    f.response :logger
    f.adapter  :patron
end

You can use any standard Faraday middleware and plugins in the configuration block. You can also initialize the transport class yourself, and pass it to the client constructor as the transport argument:

transport_configuration = lambda do |f|
  f.response :logger
  f.adapter  :patron
end

transport = OpenSearch::Transport::Transport::HTTP::Faraday.new \
  hosts: [ { host: 'localhost', port: '9200' } ],
  &transport_configuration

# Pass the transport to the client
#
client = OpenSearch::Client.new transport: transport

Instead of passing the transport to the constructor, you can inject it at run time:

# Set up the transport
#
faraday_configuration = lambda do |f|
    f.instance_variable_set :@ssl, { verify: false }
    f.adapter :excon
end

faraday_client = OpenSearch::Transport::Transport::HTTP::Faraday.new \
    hosts: [ { host: 'my-protected-host',
                port: '443',
                user: 'USERNAME',
                password: 'PASSWORD',
                scheme: 'https'
            }],
    &faraday_configuration

# Create a default client
#
client = OpenSearch::Client.new

# Inject the transport to the client
#
client.transport = faraday_client

You can also use a bundled Curb based transport implementation:

require 'curb'
require 'opensearch/transport/transport/http/curb'

client = OpenSearch::Client.new transport_class: OpenSearch::Transport::Transport::HTTP::Curb

client.transport.connections.first.connection
# => #<Curl::Easy http://localhost:9200/>

It's possible to customize the Curb instance by passing a block to the constructor as well (in this case, as an inline block):

transport = OpenSearch::Transport::Transport::HTTP::Curb.new \
    hosts: [ { host: 'localhost', port: '9200' } ],
    & lambda { |c| c.verbose = true }

client = OpenSearch::Client.new transport: transport

You can write your own transport implementation easily, by including the {OpenSearch::Transport::Transport::Base} module, implementing the required contract, and passing it to the client as the transport_class parameter -- or injecting it directly.

Serializer Implementations

By default, the MultiJSON library is used as the serializer implementation, and it will pick up the "right" adapter based on gems available.

The serialization component is pluggable, though, so you can write your own by including the {OpenSearch::Transport::Transport::Serializer::Base} module, implementing the required contract, and passing it to the client as the serializer_class or serializer parameter.

Exception Handling

The library defines a number of exception classes for various client and server errors, as well as unsuccessful HTTP responses, making it possible to rescue specific exceptions with desired granularity.

The highest-level exception is {OpenSearch::Transport::Transport::Error} and will be raised for any generic client or server errors.

{OpenSearch::Transport::Transport::ServerError} will be raised for server errors only.

As an example for response-specific errors, a 404 response status will raise an {OpenSearch::Transport::Transport::Errors::NotFound} exception.

Finally, {OpenSearch::Transport::Transport::SnifferTimeoutError} will be raised when connection reloading ("sniffing") times out.

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transport_options.md

transport_options.md

OpenSearch::Transport

Setting Hosts and Ports

Authentication

Logging

Custom HTTP Headers

Setting Timeouts

Connection Selector

Retrying on Failures

Reloading Hosts

Transport Implementations

Serializer Implementations

Exception Handling

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transport_options.md

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transport_options.md

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OpenSearch::Transport

Setting Hosts and Ports

Authentication

Logging

Custom HTTP Headers

Setting Timeouts

Connection Selector

Retrying on Failures

Reloading Hosts

Transport Implementations

Serializer Implementations

Exception Handling